Easy opening closure, container provided with such closure, and apparatus for producing such closure

ABSTRACT

The invention relates to an easy opening closure, comprising a closure having a folding rim and a circumferential score line having a score residual (t) the thickness of the closure in the score line, enclosing a removable central closure part; and a tab connected to the central closure part, which score line has a pop zone in which the tap pops a section of the central closure along the score line and the pop zone comprising a pop ignition zone adjacent to the tab, in clock-wise and anti-clock-wise direction subsequent tear zones in which using the tab the central closure part is torn off from the closure along the score line and eventually looses from the closure, wherein the tear zones comprise each a tear ignition zone adjacent the respective pop zone, and wherein the score residual (t) the tear ignition zones is reduced relative to the score residual in the pop ignition zone, to a container, provided with such easy opening closure and to an apparatus for producing the same.

The present invention relates to an easy opening closure, to a containerprovided with an easy opening closure, and to an apparatus for producingsuch an easy opening closure.

An easy opening closure is a metal closure in which an opening may beformed by using one or more fingers and without the requirement forusing tools. An easy opening closure comprises a closure having afolding rim to be connected to an open end container, and acircumferential score line provided in the closure and enclosing aremovable central closure part. This central closure part is providedwith a tab which is connected using a rivet to the central closure part.This tab is used for providing an opening in the easy opening closure bypopping, tearing off and subsequently loosing the central closure partalong the score line from the remaining part of the closure.

In the first part of the manual opening operation a finger or nail isinserted between the central closure part and the free end of the tab,whereafter that end of the tab is lifted. This lifting movement resultsin a popping of a section of the central closure as the other lever endof the tab pushes that section inwardly and thereby breaks that sectionloose of the central closure along the score line and folds that sectioninto the internal of the container provided with the closure. Thepopping starts in the pop ignition zone which is adjacent or below thepop end of the tab which is remote of the free end of the tab. Duringlifting of the tab free end the pop end folds the section inwardly. Thislifting stops when the free end of the tab extends upwardly from theclosure (see FIG. 2). At the end of the popping operation the centralclosure part is broken loose from the remainder of the closure over thepop zone of the score line. At this place between the scored and intactscore line are the transitions between the pop zone and the adjacenttear ignition zones. The latter are part of the tear zones.

In the second part of the opening operation this upwardly extending freeend of the tab is gripped by one or more fingers and the other part ofthe central closure is torn loose along the score line. During thistearing operation the score opens simultaneously in a clock-wise andanti-clock-wise direction of the score line.

The final part of the opening procedure is the tearing off the centralclosure at the diametral position to the pop ignition zone.

The tab popping of the closure takes place in the pop zone. The tearingin the clock-wise and anti-clock-wise direction results in the tearzones. The tearing loose of the central closure part from the remainderof the closure takes place in the so called hinge zone.

In general, a metal easy opening closure has a thickness of about 0.17to 0.30 mm. A more specific value of this thickness is dependent on thetype of metal of the closure, such as aluminum and tin plate. In thescore line the thickness over the closure score, the so called scoreresidual is generally in the range of 50-90 μm again dependent on thetype of metal used and the content of (pressure in) the container. Thescore residual is conventionally transversally measured in the scoreline. In a practical embodiment the score residual resides between scorelines formed in both surfaces of the closure. If these score lines arenot aligned, then the score residual is measured as the shortestdistance between the two score lines. In addition, both sides of theeasy opening closure is provided with a lacquer having a thickness ofabout 0.01 mm. The easy opening closures may be produced at high speedup to 400-500 closures per minute.

The first lift and popping of the easy opening closure using the tabgenerally requires a popping force. For a tin plate closure of 73 mmdiameter this popping force is of about 15-25 N. The tearing off in thetear ignition zones over the clock-wise and anti-clock-wise directionsby tearing the tab requires initially a maximum tear force of 30-60 N.When the tearing progresses along the score line the tear forcegradually decreases. The total loosing of the central part of theclosure requires some force.

The dimensions of the score residual in the pop ignition zone of theeasy opening closure are selected such that it is abuse-proof to anundesired popping of the closure by the tab when on the pop end of thetab a force is affected, such as by end wall stored closures in whichorientation an endwall may press on the pop part of the tab.Furthermore, a container provided with an easy opening closure maycomprise a pressurized (carbonated) beverage and therefore the easyopening closure as a whole should be able to withstand a burstpressureof about 3-5 bar.

The present invention has for its object to provide an easy openingclosure which possesses an improved handling in that the openingprocedure requires less tear force, in particular a smaller initial tearforce.

This is obtained with an easy opening closure according to the inventionhaving a curl rim and a circumferential score line having a scoreresidual (t) over the thickness of the closure in the score line,enclosing a removable central closure part; and a tab connected to thecentral closure part, which score line has a pop zone in which the tabpops a section of the central closure along the score line and the popzone comprises a pop ignition zone adjacent to the tab, in clock-wiseand anti-clock-wise direction subsequent tear zones in which using thetab the central closure part is teared off from the closure along thescore line and eventually looses from the closure, wherein the tearzones comprise each a tear ignition zone adjacent the respective popzone, and wherein the score residual in the tear ignition zones isreduced relative to the score residual in the pop ignition zone.

The invention is based on the insight that by reducing the scoreresidual in the tear ignition zone the initial and highest tear force isreduced and the easy opening closure still meets the requirements forburst pressure and is still abuse-proof.

The reduction in score residual is maximum at least in that part of thetear ignition zone, which is adjacent to the respective pop zone. Forreasons that after popping and at the start of the tearing operation,scoring starts here at the highest tear force. Over the length of thetear ignition zone the score residual may be reduced to a maximum level(that is to a smallest thickness) or may gradually increase from amaximum reduced plateau level, that is the reduction will graduallydecrease.

The end of the pop zone and the start of the tear ignition zone isdependent on the design of the easy opening closure and on the manner inwhich the popping operation has been carried out. When the poppingoperation has not been carried out to its full extent and subsequentlythe tearing operation is started a high tear force may be appreciatedduring the scoring of the score line in the pop zone. Therefore, it ispreferred that the score residual is reduced in a part of the pop zoneadjacent to the tear ignition zone.

The effect of the invention is appreciated when the reduction in scoreresidual is maximum at the beginning of the tear ignition zones. Thisreduction in the score residual may have the form of an abrupt step ormay gradually decrease over a part of the pop zone, but reaches themaximum at least at the transition between the pop zone and the adjacenttear ignition zone. This reduction in score residual (t) is relative tothe score residual in the pop ignition zone, which is generally having ahigher or highest score residual in order to impart the easy openingclosure with abuse-proof properties.

The reduction in score residual which results in an appreciation of alower tear force is generally such that the maximum tear force isreduced as from 1N (0.2 lbs), such as 1-15N (0.2-3.3 lbs), reductions inmaximum tear force of 1-10N (0.2-2.2 lbs) or 1-8N (0.2-1.8 lbs) arefeasible within the ghist of the present invention, all in comparisonwith an easy opening closure which is not provided with the inventivereduction of score residual in at least the tear ignition zones.

The score residual may be reduced over the score line length in the tearzones, but it may be sufficient that it is only reduced in at least thefirst part of the tear zone. This reduction is relative to the mid partof the score line in the pop zone because at the interface between thepop zone and tear zone the residual may already be reduced such that atthe start of the tear zone the residual score is maximum reduced, thesight where the highest tear force is initially required.

The reduction in score residual is generally maximum 25 μm. Practicallythe reduction is in the range of 5-15 μm. Good reductions in initialtear force are obtainable at 6-9 μm, such as 7-8 μm. This in comparisonto the score residual in at least the pop ignition zone where the scoreresidual is generally in the range of 60-90 μm, such as 65-80 μm, 70-85μm and 70-80 μm.

In a preferred embodiment the score residual in the pop ignition zone ishigher than in the remainder of the pop zone. Accordingly, the pop forcefor the initial popping the central closure part is increased but to alevel which is still below the maximum initial tear force.

The formation of the reduced score residual is critical in view of theburst pressure and the requirement for abuse-proof. In a preferredembodiment the reduction in score residual is at least partly formed bya score in the surface of the public side of the closure. A variation inthe reduced score residual in at least the tear ignition zones isminimal if the reduction in score residual is at least partly formedbetween a score in the public facing surface and a score in the surfaceof the product side of the closure (see FIG. 3B).

An other aspect of the invention relates to a container which isprovided with an easy opening closure of the invention. In thiscontainer its end opening is connected to the rim of the easy openingclosure by a folding operation of the closure rim and the container rim.

Finally, the invention relates in an other aspect to an apparatus forproducing such easy opening closure. This apparatus is provided withparticular means for forming the reduced score residual. To that extentthe apparatus is characterized in that it comprises a tool for forming ascore in a surface of the closure which has a larger thickness in a toolsection for forming the reduction in the score residual. In a preferredembodiment the apparatus comprises a lower anvil and the score is formedin the surface of the product side of the closure.

Mentioned and other advantages and characteristic features of the easyopening closure, a container provided therewith and an apparatus forproducing the closure are illustrated in the following figuresillustrating embodiments of the invention although the invention is notconsidered to be restricted thereto. In the figures:

FIG. 1 shows a top view of an easy opening closure according to theinvention;

FIG. 2 illustrates the popping operation of the closure;

FIGS. 3A and 3B show two embodiments of the apparatus used for producingthe opening closure; and

FIG. 4 shows the score residual of the easy opening closure of theinvention over the clock-wise or anti-clock-wise direction.

FIG. 1 shows an easy opening closure 1. The closure 1 comprises a curlrim 2 which extends over the circumference of the closure 1. Radiallyinwardly of the rim 2 is provided a score line 3 which encloses aremovable central closure part 4. In cross section the central part 4has a substantially terrass form. The central part 4 is provided with atab 5 which is connected by a rivet 6 to the central part 4. The tab 5has a first free end 7 with an opening 8 and a pop end 9.

The score line 3 comprises several zones. A pop ignition zone 10 wheredue to a levering action of the tab 5 the pop end 9 of tab 5 pops thecentral part 4 inwardly by scoring alone the score line 3. Due to anundesired action on the pop end 9 by a load an undesired interaction ofthe pop end with the score results in an abusive opening of the score.This pop ignition zone 10 lies within the lines 11 and 12 and forms partof the pop zone which lies between the lines 13 and 14. These lines 13and 14 are defined by a cord 38 extending between the points 39 and 40where the scoring of the score line 3 stopped at the end of the poppingoperation by lifting the tab 5 (see FIG. 2). The pop zone is followed bya tear ignition zone 15 in clock-wise direction and tear zone 16 inanti-clock-wise direction and is limited by the lines 14 and 17 and thelines 13 and 18 respectively. In the tear ignition zones 15 and 16highest tear forces are encountered. The length of the tear ignitionzones 15 and 16 corresponds to a length over which the tear forcesreduces to 60-90%, such as 70 or 80% of the maximum value for the tearignition. The tear ignition zones 15 and 16 are followed by the otherparts of the tear zone 19 and 20 and meet in an optional hinge zone 21.

FIG. 2 shows the end of the pop procedure in which the tab popped thescore line 3 thereby forming an opening 22. The tab 5 is extendingupwardly with its end 7. Over the pop zone between the lines 13 and 14the central closure part 4 is loose from the remainder of the closure 1.

FIG. 4 shows the reduction of the score residual t over the length ofthe score line 3. The reduction of the score residual in the popignition zone 10 is nil. In the tear ignition zone, in particular at thetransition 24, the reduction of the score residual is maximum andamounts 8 μm in this embodiment of the closure and forms a plateau 23.In both circumferential directions the score residual t graduallydecreases to the plateau 23 in the pop zones (between the respectivelines 12 and 14, and 11 and 13) and in the tear ignition zones 15 and 16gradually increases (curve A). In an other embodiment (for instance whenthe content of the container is not pressurized) the reduction of thescore residual may stay substantially constant in the tear zones 19 and20 but decrease gradually towards a hinge zone 21 where the scoredcentral point is broken off from the closure (curve B).

In the pop ignition zone 10 the residual may be increased to about 70 μmto make the closure more abuse-proof. In the hinge zone 21 the residualmay also be increased (for instance to about 100-150 μm in order to makethe closure more injury-proof.

Finally, FIG. 3 shows an apparatus 26 for producing an easy openingclosure of the invention. The apparatus comprises a score die 27 andlower anvil 28. The lower anvil 28 has a flat anvil surface 29. Theupper anvil 27 has an sharp end 30 for making the score line 3 in theclosure 1. The score residual (t) shown in the tear ignition zone 25.

FIG. 3B shows an other apparatus 31 for producing an easy openingclosure 1 according to the invention. This apparatus 31 comprises ascore die 27 with the sharp end 30, but comprises in addition a loweranvil 32 which has a rounded anvil surface 33.

The closure 1 produced in the apparatus 26 has a public facing surface34 in which the score line 3 is produced and a product facing surface 35which is flat in the region of the score 3.

The closure 1 produced with the apparatus 31 of FIG. 3B has a score 3 inthe public facing surface 34 and a score 36 in the product facingsurface 37. In the apparatus 31 the scores may be formed in one step orin two consecutive steps.

Using both apparatuses 26 and 31 of the invention at high speedproduction closures of the invention may be produced at standardtolerances.

1-12. (canceled)
 13. An easy opening closure comprising a closure havinga folding rim and a circumferential score line having a score residual(t) over the thickness of the closure in the score line, enclosing aremovable central closure part; and a tab connected to the centralclosure part, which score line has a pop zone in which the tab pops asection of the central closure along the score line and the pop zonecomprises a pop ignition zone adjacent to the tab, in clock-wise andanti-clock-wise direction subsequent tear zones in which using the tabthe central closure part is torn off from the closure along the scoreline and eventually looses from the closure, wherein the tear zones eachcomprise a tear ignition zone adjacent the respective pop zone, andwherein the score residual (t) in the tear ignition zones is reducedrelative to the score residual in the pop ignition zone.
 14. The easyopening closure as claimed in claim 13, wherein the reduction in scoreresidual (t) is maximum at least at the transition between the pop zoneand the adjacent tear ignition zone.
 15. The easy opening closure asclaimed in claim 13, wherein the reduction in score residual (t)decreases gradually from the transition.
 16. The easy opening closure asclaimed in claim 13, wherein the score residual (t) is reduced in a partof the pop zone adjacent to the tear ignition zone.
 17. The easy openingclosure as claimed in claim 13, wherein the reduction in score residual(t) is maximum 25 μm.
 18. The easy opening closure as claimed in claim13, wherein the maximum tear force is reduced from 1N (0.2 lbs).
 19. Theeasy opening closure as claimed in claim 13, wherein the reduction inscore residual (t) is at least partly formed by a score in the surfaceof the public side of the closure.
 20. The easy opening closure asclaimed in claim 13, wherein the reduction in score residual (t) is atleast partly formed by a score in the surface of the product side of theclosure.
 21. The easy opening closure as claimed in claim 13, whereinthe tear zones meet in a hinge zone having a score residual (t) at leastequal to the score residual (t) of the pop ignition zones.
 22. Acontainer, provided with the easy opening closure of claim
 13. 23. Anapparatus for producing an easy opening closure, comprising a tool forforming a score in a surface of the closure, which has a largerthickness in a tool section for forming the reduction in the scoreresidual.
 24. The apparatus as claimed in claim 23, wherein the tool isa lower anvil for forming a score in the surface of the product side ofthe closure.
 25. The easy opening closure of claim 13, wherein thereduction in score residual (t) is in the range of 5-15 μm.
 26. The easyopening closure of claim 13, wherein the reduction in score residual (t)is in the range of 7-8 μm.
 27. The easy opening closure as claimed inclaim 14, wherein the reduction in score residual (t) decreasesgradually from the transition.
 28. The easy opening closure as claimedin claim 14, wherein the score residual (t) is reduced in a part of thepop zone adjacent to the tear ignition zone.
 29. The easy openingclosure as claimed in claim 15, wherein the score residual (t) isreduced in a part of the pop zone adjacent to the tear ignition zone.30. The easy opening closure as claimed in claim 14, wherein thereduction in score residual (t) is maximum 25 μm.
 31. The easy openingclosure as claimed in claim 14, wherein the maximum tear force isreduced from 1N (0.2 lbs).
 32. The easy opening closure as claimed inclaim 15, wherein the maximum tear force is reduced from 1N (0.2 lbs).